Monoalkyl or monoaryl ethoxylates, i.e., the monoalkyl or monoaryl ethers of polyglycols, can be readily prepared, as can be the ethoxylates, themselves, i.e., the polyglycols. They are produced industrially from alcohols or phenols, respectively, and ethylene oxide. Using ethylene oxide and propylene oxide, mixed ether chains are also prepared. The properties of these compounds depend on the structure of the end-positioned alcohol, on the number of ethoxy or propoxy groups attached by condensation, and, for the polyglycols, on the molecular weight.
Because of the relationship of their properties to the requirements of the end use, such polyglycols and their monoethers are suitable, as nonionic tensides, solvents for gas scrubbing, hydraulic fluids, etc. However, their terminal OH-groups impart a certain instability, for example with respect to oxidation. This disadvantage is not exhibited by the dialkyl ethers. However, unlike the polyglycols (1,2-glycols) and their monoalkyl ethers whose preparations are easy and modifiable, the manufacture of the dialkyl ethers presents difficulties.
Dialkyl ethoxylates can be obtained, for example, by reacting monoalkyl ethoxylates with isobutene, yielding a tert-butyl alkyl ethoxylate. In the same way, the methyl ethers can be obtained according to classical methods, such as by reacting the sodium alcoholate with halogenated hydrocarbons. However, these manufacturing methods are very expensive.
It is known from U.S. Pat. No. 3,428,692 whose disclosure is incorporated by reference herein, to produce methyl ethers, namely the methyl-blocked ethoxylates, by heating ethoxylates consisting of vicinal glycols, or the monoalkyl or monophenyl ethers thereof, to 200.degree.-300.degree. C. in the presence of nickel or cobalt catalysts, preferably Raney nickel, by means of deformylation. However, in this process, mixtures are produced consisting of the desired methyl ethers and incompletely reacted ethoxylates and unidentified aldehydes, in accordance with the following reaction scheme: ##STR1##
Consequently, there is a continuing great interest in producing these monoalkyl or monoaryl methylethoxylates and dimethylethoxylates selectively and in high yields.